From The Editor | November 22, 2023

Would You Bet Your Paycheck On Tomorrow's Weather Forecast?

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By John Oncea, Editor

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Weather forecasts are correct too often to ignore and wrong too often to rely on. But they are getting better – a five-day forecast today is as accurate as a one-day forecast was in 1980. What’s driving the improvement? Observation, supercomputers, and, soon, phased array radar.

The National Oceanic and Atmospheric Administration (NOAA) predicts winter 2023-24 will be influenced by a moderate to strong El Niño. This could lead to a mild and dry winter in the northern United States and a wetter-than-average winter in the southeast.

This year, El Niño is in place heading into winter for the first time in four years, driving the outlook for warmer-than-average temperatures for the northern tier of the continental United States, according to NOAA’s U.S. Winter Outlook released today by the Climate Prediction Center — a division of the National Weather Service.

“These outlooks provide critical guidance on the upcoming season for many industries and sectors of our economy, from energy producers to commodities markets to agricultural interests to tourism,” said Sarah Kapnick, Ph.D., NOAA chief scientist. “With a strengthening El Niño and more potential climate extremes in an already record-breaking year, we’re lucky to have scientists like those at the Climate Prediction Center helping to build a Weather and Climate-Ready Nation by providing critical operational seasonal climate predictions.”

So, there you go. Plan accordingly.

Under The Weather

NOAA uses various tools and methods to forecast the weather. It collects data from satellites, weather stations, buoys, ships, radar systems, and other sources worldwide. This data includes temperature, humidity, wind speed, air pressure, and more.

Powerful supercomputers are also used to run mathematical models that simulate the Earth’s atmosphere. These models take in observational data and use complex equations to predict how the atmosphere will evolve. They divide the atmosphere into a grid and calculate changes in weather variables at each grid point over time.

Instead of relying on a single model run, NOAA often uses multiple models and variations (ensembles) to account for uncertainty. By running different simulations with slightly varying initial conditions or model setups, they can provide a range of possible outcomes.

NOAA’s fleet of satellites provides crucial real-time imagery of weather patterns, cloud cover, temperature, and more. This information helps meteorologists observe and track weather systems as they develop and move.

While technology plays a significant role, experienced meteorologists interpret the model outputs, satellite data, and other information. Their expertise helps refine forecasts, especially in complex or rapidly changing situations. Weather forecasts are continuously updated as new data comes in and NOAA validates and improves their models based on past performance and ongoing research, constantly refining their forecasting methods.

PAR: The Future Of Forecasting

“NOAA’s National Weather Service is part of a tri-agency partnership with the United States Air Force and Federal Aviation Administration to support our Nation’s weather radars,” writes NOAA. “The combined current system is the Weather Surveillance Radar 1988-Doppler system (WSR-88D), also known as NEXtgeneration RADar (NEXRAD), with 159 operational stations across the country and U.S. territories.”

The WSR-88D network has been operational since the early to mid-1990s and has been continually updated with the latest technology. NEXRAD is the primary observing system that collects data for weather prediction, including wind, precipitation, turbulence, lightning, and other environmental variables. By combining this data with forecast models, the NWS can provide daily forecasts that are crucial for public needs, including warnings and watches for severe storms, tornadoes, hurricanes, flooding, and heavy snow.

Over the past 25 years, many components of NEXRAD have been upgraded with the latest technology, but some of the major components are still original to the system. To address this, a Service Life Extension Program (SLEP) was initiated in 2015 to repair and refurbish these major components, including the signal processor, transmitter, pedestal, shelters, and generators. The SLEP is expected to be completed in 2024 and will ensure that NEXRAD remains operational until at least 2035. In the meantime, NOAA is exploring various options for NEXRAD beyond 2040, which could include another Service Life Extension Program, a rotating dish replacement system, or Phased Array Radar (PAR).

“Over the past 20 years NOAA/OAR, industry, and academia have made significant advancements in PAR research, development, and technology for weather surveillance and other applications,” NOAA writes. “Because of these advancements, PAR is a leading contender in the solution for replacing the legacy system.”

PAR is an advanced scanning technique that can quickly and efficiently scan the atmosphere at a 90-degree sector angle in just 60 seconds. This is a vast improvement over the existing system which takes 4-5 minutes to scan the same volume. It provides a more precise representation of rapidly evolving severe weather conditions, enabling forecasters to better understand atmospheric conditions and issue more accurate and timely warnings.

With PAR, low-level wind observations can be made from volume coverage patterns, providing a top-to-bottom profile of storms approximately every minute. This can help analyze storm spin-up and assimilate wind data more accurately, considering factors such as updraft forcing, size, strength, and storm track. These technical improvements can significantly advance forecast accuracy on shorter timescales for acute extreme weather, such as tornadoes, severe weather, and flash flooding. This information is critical for aviation, transportation sectors, and emergency management.

According to NOAA, “PAR uses an integrated, flat antenna which contains an array of thousands of individual elements that scan electronically, rather than mechanically, so the radar can re-scan areas very quickly and adapt to different scenarios (such as targeted scanning during severe weather). This switch to array technology versus dish technology also has the potential to allow engineers and technicians to isolate and maintain radar components without taking the entire system offline, which may reduce maintenance downtime.”

NOAA’s National Weather Radar Testbed (NWRT) is a PAR that is being tested in Norman, OK, and NOAA also has made advancements in PAR technology for weather surveillance. NOAA’s National Severe Storms Laboratory (NSSL) installed a proof-of-concept system called the Advanced Technology Demonstrator (ATD) in 2018. The ATD is a dual-polarized PAR that evaluates dual polarization calibration and performance on PAR technology. The ATD also demonstrates advanced scanning techniques for weather radars using PAR.

As noted, PAR is a leading contender to replace the legacy system. Congress provided $30 million to procure a demonstration system for a dual-polarization PAR. The demonstration system will assess advanced techniques to meet NOAA's future weather radar requirements.

“A careful evaluation of PAR technology and other alternatives is underway to determine the future of NOAA’s weather radar. As part of that evaluation, the Weather Program Office, in collaboration with the National Severe Storms Laboratory (NSSL) will deliver to the NWS timely, state-of-the-science information to inform their decision-making process for the next operational weather radar system,” NOAA writes. “This includes information on PAR weather surveillance technology and an understanding of the criteria needed to transition PAR technology to operations.”

The National Weather Service will use this information to decide on the future of NEXRAD by 2030, with a target date of implementing a radar follow-on plan by 2040 that helps improve operational weather forecasting with better, more accurate weather warnings to reduce loss of life and property damage.